How do women with eating disorders overpower their bodies' urge to eat? New research has found the illness actually alters the way their brains work.

It was proven recently that hunger is the most powerful motivational force humans face—even stronger than thirst, anxiety, fear, and social connection. This has led many experts to wonder how it is that individuals with anorexia can maintain long-term food restriction, without their bodies and brains rebelling by forcing them to eat.

Researchers at the University of Colorado may have the answer. They have found that the brain processes of women with anorexia and bulimia nervosa actually morph, allowing them to override the (otherwise all-consuming) urge to consume food.

When they taste something sweet, there is an automatic response that says: 'Do not do that.'

In healthy people, the brain receives messages from the body, then tells the body to eat so that it doesn't starve. These signals from the body, including factors such as low blood sugar, are collected by the hypothalamus—the part of the brain that controls hunger, among other things.

Hunger signals are then sent to the areas in the brain where executive function takes place, like planning and decision-making. At this point, other motivators might play a role in what and whether we eat, such as not eating out of a desire to lose weight—or eating because we like the look of the food that's available.

The results of this new research indicate that the processes described above are reversed in people with eating disorders, which may be the neurological reason they are able to ignore hunger more easily. Published in the journal Translational Psychiatry, the study looked at the brain function of 26 healthy women, 26 women with anorexia, and 25 women with bulimia nervosa, using sugar tasting.

Dr Guido Frank is the study's author and an associate professor of psychiatry and neuroscience at the University of Colorado. "In the healthy women, the information flow while tasting sugar went from the hypothalamus to the areas that drive motivation," Dr Frank tells Broadly. "In the women with anorexia or bulimia nervosa the information flow went in the opposite direction."

In other words, in women with anorexia and bulimia nervosa, the information was sent to the motivation area of the brain first, indicating an ability to ignore signals to eat from the hunger-driving hypothalamus.

"What we believe is that fear of weight gain overrides signals from the hypothalamus," says Dr Frank. "When [anorexics] taste something sweet, for instance, there is an automatic response that says: 'Do not do that.' This is probably a learned response, but a response that's difficult to reverse because it's anxiety driven."

This is a significant advancement in the study of eating disorders, and should help inform treatment, Dr Frank says. Future research may involve investigation into what brain chemicals are involved in these processes, in order to develop a medication regime to facilitate treatment.

Dr Frank is currently studying youth with eating disorders, to see whether these findings will hold in minors. "My speculation would be that we find similar results," he says.

And in men? "With men with eating disorders it is very difficult to recruit numbers that would allow for reliable results... We are doing that as well, but this is a very long process."